1. Field of the Invention
This invention relates to an apparatus for mixing a fluid, such as a heavy oil, and particles, such as a catalyst, heated at elevated temperatures.
2. Prior Art
Reaction systems are known in which solid particles, as a catalyst or a heat medium, are brought into contact with a reactant. Moving bed type reactors are a typical example of such reaction system, which reactors are classified into those utilizing a concentrated fluidized bed (bubbles-fluidized bed) and those utilizing a high-speed moving bed (fluidized bed). The high-velocity moving bed is used for a reaction in which a solid and a gas must come into contact for a short period of time. Currently, an upflow-type high-velocity moving bed reactor, a so-called "riser-type," has mainly been employed in a fluid catalytic cracking apparatus used for the production of a gasoline from a feed stock, such as a heavy oil. This reactor is capable of reducing contact time with an improvement of catalytic ability, leading to an enhancement of selectivity of a final product and suppression of unfavorable excessive cracking reactions.
Recently, a strong demand has been made for an enhancement in selective productivity of a gasoline or a light olefin, and an investigation has been conducted for use of a downflow type high-velocity moving bed reactor, which is free from back-mixing, which adversely affects an improvement of the selectivity.
When producing gasoline from a feed stock, such as a heavy oil, using a fluid catalytic cracking apparatus equipped with the existing upflow-type reactor having a high-speed moving bed, the contact reaction therein takes several seconds. In contrast, when producing a light olefin, the reaction time is required to be reduced on the order of 0.1 to 1.5 seconds. A rapid mixture of a feed stock and a catalyst and vaporization thereof at the inlet port of a reactor is indispensable, in order to conduct the contact reaction in a short period of time. Furthermore, it has become necessary to increase the recycle ratio of catalyst to oil to compensate for a reduction in conversion resulting from a shortened reaction time.
In view of this background, there has been demanded an apparatus which is capable of rapid mixture and vaporization of the feed stock and the catalyst at the inlet of the existing upflow-type reactor to form a high-speed moving bed, and which enables a recycle ratio of catalyst to oil several times greater than that (catalyst/oil ratio of 5-8) of a catalytic cracking apparatus for producing a gasoline from a feed stock, such as a heavy oil.